I tried booting Knoppix from an SD card.  I thought it would be a good idea since I have built in SD memory card readers in both my desktop and laptop systems, and both systems support boot from removable device.  
 
I got it to work, but here is the problem I encountered.  When I created the OS on the SD card using my desktop system, it would work all good and fine, but only on the desktop.  The laptop would not recognize it.  Vice versa, when I created the OS on the laptop, it worked fine there, but then the desktop wouldnt recognize it.
 
I guess I am wondering if it is a problem unique to (or at least more prone to) SD cards than jump drives (thumb drives)?
 
For reference I used the procedure from http://www.althack.com/index.php?option=com_content&task=view&id=24&Itemid=27

intersting reading guys, thanks....also for the websites